Genetic diversity within Miscanthus × giganteus: Evidence from morphological traits and ITS rDNA in European accessions

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BACKGROUND: Miscanthus × giganteus (M × g) is a sterile allotriploid hybrid (M. sacchariflorus × M. sinensis) widely used for biomass production and generally considered genetically uniform due to clonal propagation and a strong founder effect. However, phenotypic variation observed in European-grown material suggests that this assumption may be oversimplified. METHODS AND RESULTS: This study compared biometric, morphological, and genetic characteristics of four M × g accessions used for agronomy field trials in Croatia (HR), Ukraine (UA), Germany (DE), and the Czech Republic (CZ). Biometric analysis revealed that the HR accession produced 1.6-2-fold higher biomass yield, primarily associated with a 1.5-3-fold increase in sprout number. The HR accession also exhibited distinct morphological traits, including stem pigmentation and trichome presence. Sequencing of nuclear ribosomal DNA internal transcribed spacer markers (ITS1 and ITS2) identified seven polymorphic sites (four in ITS1 and three in ITS2) three of them unique to the HR accession, whereas UA, DE, and CZ displayed identical sequences. In silico comparison with reference sequences confirmed and further highlighted the marked divergence of the HR accession. Notably, variation at position 195 bp in ITS2 indicated fixation of a single ribotype in HR compared to heterozygosity in the remaining accessions. CONCLUSIONS: The results suggest the presence of limited genetic variation within M × g, despite its predominantly clonal propagation. The observed association between ITS polymorphisms and phenotypic traits in the HR accession indicates that intra-specific variation may contribute to differences in biomass performance. These findings highlight the potential for identifying and utilizing divergent accessions in future breeding and selection programs, while also suggesting that the assumption of strict genetic uniformity in M × g may require reconsideration.